Mentioned in This Article
1. What is Zakura proposing for Zcash swaps?
Developers behind Zakura, a newer version of the software that runs the Zcash network, outlined a plan on October 19 to give every ZEC swap made through the NEAR Intents service its own viewing key. The aim is to stop a future quantum computer from using a single exposed refund address to reconstruct a user's payment history. Spending keys would stay with the user, and the change could reach compatible wallets within weeks.
The proposal appeared in a new engineering post from the Zakura team. It targets a narrow but real weak point: the moment a private Zcash address is placed on a public blockchain so that a swap provider knows where to send money back if something goes wrong.
The idea is easiest to understand as compartmentalization. Instead of one master viewing key standing behind every address a user has ever shared, each cross-chain swap would be walled off from the others, so a breach of one compartment does not spill into the rest.
2. How does a NEAR Intents swap expose an address?
NEAR Intents is a service that lets users exchange tokens across different blockchains. When someone swaps private ZEC for the USDC stablecoin, the service publishes one of the user's private Zcash addresses on NEAR's public chain. The address serves as the refund destination, so unused ZEC can be returned if the trade does not complete.
The address is recorded when the deposit arrives. It stays on the public ledger even when the swap succeeds and no refund is ever needed. Anyone can read it indefinitely, which turns a routine operational detail into a permanent public record tied to the user's wallet.
For ordinary users the exposure carries little risk today. The concern is about what an attacker might be able to do with that stored address years from now, once computing capabilities change.
3. Why are the addresses safe today?
Current computers cannot extract anything useful from such an address. Each Zcash address carries a public key derived from the wallet's viewing key, using one-way elliptic-curve mathematics of the same family that protects bitcoin and ether. Going forward from key to address is easy; going backward is, for classical machines, computationally out of reach.
That one-way property is the foundation of most public-key cryptography in use across the industry. It is why publishing an address is considered harmless: the address reveals where funds can be sent, not the secret that controls or reads them.
Cross-chain services of this kind generally need some way to return funds to the original sender, since a swap can fail if prices move or liquidity runs out. Publishing a refund destination is the conventional answer, and it is the step that places a user's private-pool address in public view.
4. Why does Zcash depend on viewing keys?
Zcash is a privacy-focused blockchain that lets users hold and send ZEC in shielded form, where the sender, receiver and amount are encrypted rather than shown on the public ledger. Privacy does not mean that nobody can ever look: the design includes viewing keys, which allow a holder to read the transactions associated with an account without being able to move the funds.
Viewing keys are useful in legitimate settings. An individual may share one with an accountant, an auditor or a compliance team to prove what an account received. The same feature is what makes a leak of the key so consequential, because it unlocks the amounts and memo fields that shielded transactions are designed to conceal from everyone else.
Because several addresses can be derived from a single viewing key, the wallet experience stays simple: a user can hand out a fresh address for every payment without managing a separate secret each time. The trade-off, as the Zakura team describes it, is that all of those addresses share one point of failure.
5. What could a quantum computer change?
A sufficiently large quantum computer running Shor's algorithm, which was published in 1994, could in theory work backward from a public key to the key behind it. The algorithm is the standard example of why quantum machines are seen as a long-term threat to elliptic-curve cryptography.
The same exposure applies to early bitcoin from the so-called Satoshi era, whose public keys are already visible onchain. Google said last week that its Willow quantum chip produced near-perfect versions of a component that such an attack would require, a step toward a more capable machine.
Quantum computers able to carry out this kind of attack are probably years away, and there is no firm date. Developers across the industry are working on the problem now precisely because blockchain data is permanent: information published today can be examined by tools that exist only in the future.
Elliptic-curve schemes were adopted widely because they provide strong security with short keys, which keeps transactions compact. That efficiency is part of why networks including Bitcoin, Ethereum and Zcash rely on them, and part of why a break in the underlying mathematics would matter so broadly.
6. One key for every swap
Zcash wallets can generate many addresses that look unrelated to one another, but those addresses usually share a single viewing key. If an attacker cracked that key from one published address, they could link every payment the account has received and read the amounts and the attached memos.
Spending requires a separate key, so the funds themselves would remain protected. The damage would instead be to privacy, which is the main reason many people hold ZEC in the first place. A leaked viewing key would not let someone take coins, but it could let them see the full history of what came in.
Zakura's answer is to issue a distinct viewing key for each swap, while the spending key stays with the user's main account. Under that arrangement, an attacker who broke the refund address posted on NEAR would see only the payments tied to that one swap. The rest of the account's history would remain hidden.
Recovery from a backup is a moment when wallet design is tested, since users expect to enter a seed phrase and see their balance and history return within a reasonable time. Any scheme that undermines that expectation would meet resistance from wallet developers and from the people who rely on them.
7. Why does permanent public data raise the stakes?
Public blockchains keep a record that cannot be edited or deleted. A refund address written to NEAR's chain today will remain readable for as long as that chain exists. This differs from a conventional web service, where old data can be removed or overwritten if a risk emerges later.
Security researchers describe the resulting concern as an attacker collecting information now and decoding it once better tools are available. For a payment network built around confidentiality, that makes it sensible to limit how much any single published value can reveal, even if the machines capable of exploiting it do not yet exist.
The Zakura approach follows that principle of containment. Rather than assuming a single address will never be broken, it assumes one might be and arranges the keys so that the harm stays confined to a single swap.
8. What is the practical difficulty with many keys?
The design creates a bookkeeping problem. A wallet that has completed hundreds of swaps would hold hundreds of keys. Restoring such a wallet from a backup would require scanning the entire Zcash chain once with each key to find any refunds that arrived, a slow and resource-heavy process.
This is the kind of trade-off that often decides whether a privacy feature is adopted. A protection that makes wallets impractically slow to recover is unlikely to be switched on by default, whatever its theoretical benefits.
In plain terms, the wallet can ask the database a question and receive an answer that does not reveal what was asked. Applied here, the database serving refund information would learn nothing about which addresses a given wallet is checking, so it cannot link a user's swaps together.
9. How would private information retrieval help?
Zakura proposes a database that wallets can query using private information retrieval, a technique that lets a user fetch a record without the server learning which record was requested. The wallet asks where its refunds landed, and the database answers without learning which addresses were requested.
That removes the need for a full chain scan per key while avoiding a new leak, since a naive lookup service could itself learn which addresses belong to the same user. The approach keeps the privacy goal intact while making recovery manageable.
10. What is the rollout timeline?
No quantum computer able to recover these keys has been demonstrated. Zakura says wallets built on its open-source libraries, including Vizor, could add the feature within weeks. Hardware wallets would follow once their firmware supports it, which typically takes longer because device software must be updated and certified.
The schedule would deliver the fix before the January target that Zcash developers set earlier in October for quantum-resistant payments. That goal followed a scare in which developers discussed a so-called bunker mode. The swap-level keys therefore act as an interim layer of protection while the broader upgrade is prepared.
For users, the practical effect would be limited at first. Anyone swapping ZEC through NEAR Intents would see no change unless their wallet adds support, so the benefit depends on software makers adopting the feature and on users keeping their wallets up to date. Hardware wallet owners face a longer wait, because the devices must receive new firmware before they can handle per-swap keys.
The plan also illustrates how privacy projects are approaching quantum risk in stages. Rather than waiting for one sweeping upgrade, developers are looking for places where public exposure is greatest and adding targeted protections there, while longer-term work on quantum-resistant payments continues.
What to watch next is whether compatible wallets actually ship the feature in the coming weeks, and whether the January quantum-resistance target holds. Neither has been confirmed beyond the developers' own statements.